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Background: Type 1 regulatory T (Tr1) cells are critical players in maintaining peripheral tolerance, by producing high IL-10 levels in association with inducible T-cell co-stimulator (ICOS) expression. Whether these cells play a role in naturally acquired baked egg tolerance is unknown., Objectives: Evaluate frequencies of egg-responsive Tr1 and Th2 cells in egg-allergic children that naturally acquired baked egg tolerance (BET) versus non-egg-allergic (NEA) children., Methods: Peripheral blood mononuclear cells from 70 natural BET and 15 NEA children were stimulated for 7 days with ovalbumin and ovomucoid. By flowcytometry, egg-responsive Tr1 cells were identified by co-expression of CD49b and LAG3, and Th2 cells by expression of CD49b but absence of LAG3. Seven-day cultured supernatant was analyzed for Th1, Th2, Tr1, and Th17 cytokines by MSD., Results: Natural BET children had a higher percentage of egg-responsive Th2 cells vs. NEA children (6.75% vs. 10.35%, p = .006). No significant difference was found in frequencies of egg-responsive Tr1 cells between NEA and natural BET children (11.40% vs. 12.55%, p = .42), although Tr1-related IL-10 and IL-21 production was higher in BET children. Interestingly, egg-responsive Tr1 cells from NEA children expressed higher ICOS levels vs. natural BET children (97.90 vs. 88.20, p < .0001). Supernatant from natural BET children showed elevated levels of Th2 cytokines IL-5, IL-9 and IL-13 and Th17 cytokine IL-17A., Conclusion: Natural BET children maintain increased egg-specific Th2 responses, along with comparable proportions of egg-responsive Tr1 cells exhibiting higher IL-10 but lower ICOS expression in comparison with NEA children., (© 2025 European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.)

Primary human mast cells (MC) obtained through culturing of blood-derived MC progenitors are the preferred model for the ex vivo study of MRGPRX2- vs. IgE-mediated MC activation. In order to assess the impact of culture conditions on functional MRGPRX2 expression, we cultured CD34 + -enriched PBMC from peripheral whole blood (PB) and buffy coat (BC) samples in MethoCult medium containing stem cell factor (SCF) and interleukin (IL)-3, modified through variations in seeding density and adding or withholding IL-6, IL-9 and fetal bovine serum (FBS). Functional expression of MRGPRX2 was assessed after 4 weeks via flow cytometry. We found similar proportions of CD34 + MC-committed progenitors in BC and PB. Higher seeding densities (≥ 1x10 5 cells/mL) and exposure to IL-9 and FBS suppressed functional MRGPRX2 expression at 4 weeks, while leaving MC yield largely unaffected. IL-6 had no impact on MRGPRX2 expression. MRGPRX2-expressing MC upregulated CD63 upon stimulation with polyclonal anti-IgE, substance P and compound 48/80 at 4 weeks. Ketotifen and dasatinib but not cromolyn sodium inhibited both IgE- and MRGPRX2-dependent pathways. Our results confirm the feasibility of functional MC activation studies on PB-derived MC after a short 4-week culture and highlight the impact of culture conditions on functional MRGPRX2 expression., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Ieven, Goossens, Roosens, Jonckheere, Cremer, Dilissen, Persoons, Dupont, Schrijvers, Vandenberghe, Breynaert and Bullens.)

Background: Intense physical exercise in athletes increases the risk to develop exercise-induced bronchocontriction (EIB). We aimed to study EIB prevalence and explore methods for effective EIB screening., Methods: Three hundred twenty-seven adolescent athletes (12-18 years) performing at least 12 h of sports a week were included. The evaluation consisted of spirometry, eucapnic voluntary hyperpnoea test (EVH) to evaluate for EIB, FeNO, skin prick testing, blood sampling (serum markers of epithelial damage and mast cell activation), and questionnaires (AQUA © , ACT, ACQ, and exposure and symptom-related questions)., Results: Of all athletes, 22% tested positive for EIB (n = 72), 14% reported a previous asthma diagnosis and 40% were atopic. Eighty percent of EIB + athletes did not use any inhalation therapy. EIB + athletes were significantly younger, had decreased FEV 1 /FVC (%), and increased post-EVH-reversibility (%) post-salbutamol compared with EIB - athletes. Furthermore, EIB was significantly associated with previous asthma diagnosis and atopy. The best predictors for a positive EVH test were AQUA © score ≥ 6 (sensitivity of 78%, p = .0171) and wheezing during exercise (specificity of 82%, p = .0002). FeNO negatively and significantly correlated with maximal fall in FEV 1 post-EVH test in atopic athletes (r = -.2735, p = .0056). Maximal fall in FEV 1 was also associated with prior PM 10 exposure (p = .036). Serum markers of epithelial damage were significantly associated with training type, training intensity, EIB severity, and prior air pollution exposure., Conclusion: Our findings support the effectiveness of a systematic respiratory screening approach, including baseline questionnaires, lung function tests, and FeNO measurement, to improve EIB detection in adolescent athletes in whom respiratory response to EVH testing is associated with prior exposure to air pollution., (© 2024 European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.)

Background: Polyethylene glycol (PEG) and polysorbate 80 (PS80) allergy preclude from SARS-CoV-2 vaccination. The mechanism(s) governing cross-reactivity and PEG molecular weight dependence remain unclear., Objectives: To evaluate PEGylated lipid nanoparticle (LNP) vaccine (BNT162b2) tolerance and explore the mechanism of reactivity in PEG and/or PS80 allergic patients., Methods: PEG/PS80 dual- (n = 3), PEG mono- (n = 7), and PS80 mono-allergic patients (n = 2) were included. Tolerability of graded vaccine challenges was assessed. Basophil activation testing on whole blood (wb-BAT) or passively sensitized donor basophils (allo-BAT) was performed using PEG, PS80, BNT162b2, and PEGylated lipids (ALC-0159). Serum PEG-specific IgE was measured in patients (n = 10) and controls (n = 15)., Results: Graded BNT162b2 challenge in dual- and PEG mono-allergic patients (n = 3/group) was well tolerated and induced anti-spike IgG seroconversion. PS80 mono-allergic patients (n = 2/2) tolerated single-dose BNT162b2 vaccination. Wb-BAT reactivity to PEG-containing antigens was observed in dual- (n = 3/3) and PEG mono- (n = 2/3), but absent in PS80 mono-allergic patients (n = 0/2). BNT162b2 elicited the highest in vitro reactivity. BNT162b2 reactivity was IgE mediated, complement independent, and inhibited in allo-BAT by preincubation with short PEG motifs, or detergent-induced LNP degradation. PEG-specific IgE was only detectable in dual-allergic (n = 3/3) and PEG mono-allergic (n = 1/6) serum., Conclusion: PEG and PS80 cross-reactivity is determined by IgE recognizing short PEG motifs, whereas PS80 mono-allergy is PEG-independent. PS80 skin test positivity in PEG allergics was associated with a severe and persistent phenotype, higher serum PEG-specific IgE levels, and enhanced BAT reactivity. Spherical PEG exposure via LNP enhances BAT sensitivity through increased avidity. All PEG and/or PS80 excipient allergic patients can safely receive SARS-CoV-2 vaccines., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Occupational allergy has been described in employees working in contact with mealworms in pet stores, live fish bait or infested stored grains and recently, in mealworm farming for animal feed and human consumption. Mealworm allergens linked to occupational allergy are troponin C, cockroach-like allergen, tropomyosin, arginine kinase, early-staged encapsulation inducing- and larval cuticle proteins., Objective: We report a case of occupational mealworm allergy and studied the culprit component., Methods: Diagnosis was done by skin prick, specific IgE, basophil activation and lung function testing. Allergen purification was performed by anion-exchange chromatography and immunoblotting with patient IgE. Allergens were identified by in-gel trypsin digest and tandem mass spectrometry. Allergenicity and specificity further confirmed by IgE inhibition and passive basophil activation experiments., Results: We describe a new case of occupational mealworm allergy in a laboratory worker, with sensitization to different developmental stages and derivates of the mealworm. In basophil activation tests, the majority of patient's basophils (69%-91%) degranulated upon stimulation with the lowest concentration of mealworm extracts (0.16 µg/ml). Despite strong sensitization to mites, the patient did not show cross-reactivity to other insects. We were able to identify alpha-amylase as the main allergen and through inhibition experiments, we demonstrated that low amounts (0.1 µg/ml) of this allergen could strongly inhibit mealworm specific IgE by 79.1%. Moreover, passive BAT experiments demonstrated the IgE-alpha-amylase interaction to be functional, inducing up to 25.5% degranulation in healthy donor basophils., Conclusion: Alpha-amylase can be identified as the responsible allergen in this specific case of occupational mealworm allergy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2022 Ganseman, Ieven, Frans, Coorevits, Pörtner, Martens, Bullens, Schrijvers, Breynaert and Proost.)

The reported incidence of immediate hypersensitivity reactions (IHR) including anaphylaxis after COVID-19 vaccination is 10-fold higher than for other vaccines. Several patient groups are theorized to be at particular risk. Since specific vaccination guidelines for these patients are based on expert opinion, we performed a retrospective monocentric analysis of the tolerability of adenoviral vector and mRNA-based COVID-19 vaccines in a cohort of patients allegedly at high risk of IHR. Reactions were assessed immediately on-site by allergists during a monitored vaccination protocol and after 3-7 days through telephone interviews. The cohort included 196 patients (aged 12-84 years) with primary mast cell disease (pMCD, 50.5%), idiopathic anaphylaxis (IA, 19.9%), hereditary angioedema (HAE, 5.1%) or miscellaneous indications (24.5%). Twenty-five immediate reactions were observed in 221 vaccine doses (11.3%). Most occurred in IA or miscellaneous patients. None fulfilled anaphylaxis criteria and most were mild and self-limiting. Reaction occurrence was significantly associated with female sex. In total, 13.5% of pMCD patients reported mast cell activation-like symptoms within 72 h post-vaccination. All pediatric pMCD patients ( n = 9, 12-18 years) tolerated both mRNA-based vaccine doses. In summary, adenoviral vector and mRNA-based COVID-19 vaccines were safe and well-tolerated in patients with pMCD, HAE, and IA. No anaphylaxis was observed. The mild and subjective nature of most reactions suggests a nocebo effect associated with vaccination in a medicalized setting. Patients with pMCD could experience mild flare-ups of mast cell activation-like symptoms, supporting antihistamine premedication.